1. Field of the Invention
The present invention relates to an emulsion ink for a stencil printing (hereinafter referred to as stencil printing emulsion ink). More specifically, the present invention relates to a stencil printing emulsion ink which has an excellent emulsion stability, drying property, and temperature suitability, has a high print concentration when printed, and has a reduced bleeding and strike through.
2. Description of the Prior Art
In a stencil printing,first a plate-making is carried out by using a stencil printing sheet having perforated portions and then an ink is extruded through the perforated portions to print the surface of a body such as a piece of paper to be printed. This stencil printing is easy in preparation of the plate-making and, thus, used in diversified applications.
As for the stencil printing, water-in oil (W/O) type emulsion ink is generally used, and a pigment is contained as colorant (coloring agent) in the oil phase of W/O type emulsion ink (Unexamined Japanese Patent Publication Nos. 61-255967, 64-14284, 4-132777, and 5-117565).
When W/O type emulsion ink is printed on the surface of a body such as a paper to be printed, an oil phase which is an outer phase of the emulsion will first permeates into the body and then a water phase which is an inner phase of the emulsin will permeates into the body or splash on the body.
Since the pigment is contained in the oil phase in conventional W/O type emulsin ink, the permeation of the ink is slow.
A resin component is contained in the oil phase in conventional W/O type emulsion ink for dispersing the pigment in the oil phase and for improving the fixation of the pigment on the surface of the body. However, a high molecular compound ia generally used as the resin component in the prior art, and thus, the permeation of the ink becomes slow; the bleeding of the ink is liable to occur even it permeated; ink components such as a pigment permeates into the inner part of the body; and the striking through of the ink readily occurs.
Further, the viscosity stability of the ink to temperature fluctuation is difficult to secure since the resin component contained in the oil phase suffers a large viscosity change to temperature.
On the other hand, while it is necessary to use a dispersant (dispersing agent) to stably and finely disperse a water-insoluble colorant such as a pigment in the water phase, emulsion is liable to be collapsed or broken and thus a stable W/O type emulsion ink can not be obtained when the dispersant exists in the water phase.